ZrB2-based composites toughened by as-received and heat-treated short carbon fibers

In order to improve the fracture toughness of ZrB2 ceramics, as-received and heat treated short carbon fiber reinforced ZrB2-based composites were fabricated by hot pressing. The toughening effects of the fibers were studied by investigating the relative density, phase composition, microstructure and mechanical properties of the composites. It was found that the densification behavior, microstructure and mechanical properties of the composites were influenced by the fibers' surface condition. The heat treated fiber was more appropriate to toughen the ZrB2-based composites, due to the high graphitization degree, low surface activity and weak interfacial bonding. As a result, the fracture toughness of the composites with heat-treated fiber is 7.62 ± 0.12 MPa m1/2, which increased by 10% as compared to the composites with as-received fiber (6.89 ± 0.16 MPa m1/2).